Centrifugal blower wheels may be constructed from a strip of sheet metal by punching out the blades from the strip in the form of louvers which leave the edges of the strip intact. In the alternative, individual blades may be stamped and cut from the strip and a blower wheel may be assembled from a group of these individual blades by securing opposite ends of the blades together so that they are permanently fastened in proper operative relation. The present invention is concerned with assembling a plurality of individual blades into a predetermined circumferentially spaced relationship about a central axis corresponding to the spaced blade relationship in a finished blower wheel.
In the past, centrifugal blower wheels, such as those used to draw air through furnaces and air conditioners and the like, have frequently been assembled almost entirely by hand. The usual methods of manufacturing blower wheels require mounting individual blades on a fixture in a predetermined relationship corresponding to the blade positioning in the finished blower wheel and then attaching rims or end rings to flanges at opposite ends of each blade while the blades are held in the fixture. The fixture is then removed and replaced by a center disc for mounting the blower on a drive shaft.
One means for attaching blades to a rim is by holding the rim adjacent to flanges at opposite ends of each blade and then spinning the composite structure in a machine which crimps a portion of the end ring around the blade flanges. Securing means such as welding, riveting or the like also may be employed. However, before the blades can be secured to end rings, rims or the like, they must be properly positioned. Although machines have been developed in the past to fasten plural blades to end members while the blades are held in a fixture, many prior art methods of manufacture require manual handling of the blades to place them in the fixture.
There have been only a few suggestions of apparatus for automatically handling individual blades so as to properly position the blades for application of an end ring or the like. For example, see U.S. Pat. Nos. 2,996,788 and 3,186,068 to Austin, et al., U.S. Pat. Nos. 2,651,830 and 2,651,837 to Wilken, et al., and U.S. Pat. Nos. 3,253,318 and 3,305,912 to Wentling, et al., the entire contents of said patents being incorporated herein by reference. Such prior art machines involve complicated operations and complex components with large numbers of machined parts which are expensive to manufacture and/or maintain. In addition, the relatively large number of moving and cooperating parts in combination with loosely held blades can cause misalignment and/or binding of blades which result in frequent shutdowns to clear up jammed blades and/or components. Furthermore, loose blades can cause misfeeds which leave a vacant position in the fixture which first must be noticed by an operator and then filled by hand before the blades are permanently attached to a rim if a defective blower wheel is to be avoided.
The foregoing disadvantages and problems with prior art devices are alleviated by the present invention.